FAME content of fuel

good day all, This will be my first post.
I serve aboard a tugboat with Cat C9 genertaors. Of late we are getting problems with clogged fuel filters.
The fuel is not overly dirty and is not stored for long periods. there is none of the usual signs of bacterial issues such as smell or jelly in filters at regular changes with cat supplied fuel filters. Service engineer has pointed to high fuel pressure and stated pressure should not exceed 700Kpa.New filter runs at 540Kpa but in a matter of days pressure has increased and again needs changing. we use ULS direct from a local UK valero refinery via reputable fuel distributor lorry.
Our fuel loads of 31m3 are all lab tested and it appears these problems originated when the lab started to comment on High Fame number in excess of 7%. Reading elsewhere this has been a problem for farmers but often assosiated with increased bug activity due to the fatty components. the FAME is a result of the addition of biofuels increasingly required by national legislation in all refined fuels?
And how did you deal with it. It would seem buying shares in a Cat filter supplier would be the best move!
My question is has anyone else had problems with filters, but not bug related

Is this happening on both gens? Are you measuring the pressures by gauges or relying on the ECM sensors?

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I suggest to check if your gauge is correct. Then if the micron of your filters is correct.

Same problem on all 3 sets. Pressure reading from control screen sensors of all 3 different sets. Different pressure gauges also recording the obstruction, but not in red zone.

Did you cut any of the filters open?
Do you have any fuel segregated from previous bunkering? Do a side by side visual in glass jars? Side by side run through filter paper.

Had similar problems with a batch of MGO from Cape Town. Compared to crystal clear (whatever tint) of typical MGO this was darker and not clear, near cloudy, couldn’t see through it. But no visible solids.

What came out in the filters was a very fine dark deposit. So fine did not see individual particles only pattern of varying shades of gray/black. I assumed the fines were on the hard side since they didn’t smear on the paper.

Sent second sample to Veritas. I was thinking we had a compatibility problem since we recently switched to tanks with that batch. Veritas said they couldn’t see a problem even on retest.

In our case the transfer pump discharge filters were the ones affected. This was upstream of settler, purifier, day tank and engine spin-on filters.

My research at the time started leading me to the FAME content as well but never confirmed. Bad news was no way around it just burned more filter elements until the fuel was gone.

Do you have any way to batch filter before getting to the day tank?


We bunker to quarantine tanks and wait for fobas test results before adding to double bottom, and then purify to day tanks. Have cut a filter open, but no obvious deposits. Will try your suggestion of filter papers, possibly test each tank individually.

A little reading up on this it certainly looks like it could be the high FAME % causing your filtration issues. As you commented the Ag industry has noticed this for a while. And it looks like even “reputable” suppliers in the UK are permitted by regulation up to 7%, (although you said your test were showing higher.) I had a problem previously with frequently clogging filters but tests showing no bacteria growth and now I’m left wondering if I missed looking at this as a possible cause.

I like KPChief’s suggestion of batch filtering, as simple as an offline filter cart on the tank just so that you at least keep the problem to before the engine side. You still might need to stock up on filters.

It would also be worth asking your Cat rep if they suggest a different filter model for fuel with high FAME content.